This invention relates to a device for use in the surgical treatment of human or non-human animals. In particular, it is concerned with a device for use in controlling excessive bleeding from severed tissue during surgical procedures, especially on the patient""s liver.
It is well known that raising the temperature of body tissue tends to reduce blood flow within the tissue. If the temperature is raised by 20-30xc2x0 C. above normal, blood flow within the tissue is greatly diminished.
In surgical procedure performed on deep-seated body tissues and organs, e.g. the liver, blood loss from severed tissue can be a serious problem. There is an obvious need for a device which can assist in limiting such blood loss and, as indicated above, this can be achieved by means of the application of heat. Widespread heating can be achieved relatively easily, but this is not desirable. Very localised heating is required in order to minimise damage to surrounding tissues. In liver surgery, local heating of the liver is ideally required in a tissue volume approximately 5 cm long by 2 cm wide by 4 cm deep; this volume is centred on the planned point of incision. Furthermore, it is important for the local elevation of temperature to be achieved quickly just prior to commencing the surgical procedure.
U.S. Pat. No. 4,974,587 discloses a device for heating biological tissues, comprising a microwave generator and an array of electro-magnetic EM energy applicators being microwave antennae or LCF capacitance type electrodes attached to an envelope filled with a high dielectric fluid. The electrodes are inserted into tubes on the surface of the envelope. This insertion process may be controlled by a positioning unit.
EP 0 073 709 discloses a device for generating localised heating in body tissues, the source of microwave being in the form of a cylindrical waveguide.
The present invention aims to provide a device for providing localised heating of a selected region of body tissue prior to surgical incision of that tissue.
According to one aspect of the present invention, there is provided a device for generating localised heating in a selected body tissue, wherein the said device comprises an applicator including a source of microwave radiation, characterised in that:
(A) the source of microwave radiation is in the form of a waveguide;
(B) the applicator includes an array of retractable needles arranged so as to extend from one face of the applicator;
(C) the waveguide and the array of needles, when extended, define a volume whose dimensions correspond to those of the tissue volume which is to be heated; and
(D) in operation, the array of needles serves to confine the irradiated microwave energy field emanating from the applicator.
The invention also provides the use of the device as defined above for restricting the loss of blood during a surgical procedure on the human or animal body.
According to another aspect of the present invention, there is provided, in the surgical treatment of the human or animal body, a method of controlling excessive bleeding, the method comprising inserting an array of needles into the tissue or organ being treated; and applying microwave energy to the region undergoing treatment for a time sufficient to raise the temperature of said tissue or organ by 20-30 degrees C.
Conveniently, the source of microwave radiation is in the form of a rectangular waveguide whose dimensions correspond to those of the tissue volume which is to be heated. The waveguide is preferably generally rectangular in form, the array of retractable needles being positioned around the periphery of the waveguide.
The device may include a needle advance mechanism including a collar to which the needles are secured; movement of said collar may be actuated by a solenoid mechanism.
In operation of the device, the needles will be advanced from the body of the applicator into the tissue which is to be heated so that the needles function as a extension of the waveguide; in this way, the applicator will direct the required microwave energy into the appropriate tissue volume prior to surgery. When the heating process is completed, the needles are retracted back into the body of the applicator.
Generally, the needles will be disposed mutually parallel, they can conveniently be formed of steel.
Theoretical calculations show that, in order to raise the temperature of body tissues by 30xc2x0 C., an applicator operating with 100% efficiency would need to deliver about 10 watts of microwave power, assuming that the volume to be heated is 40 cm. For a typical biological tissue such as muscle, this temperature rise would be achieved in approximately 10 minutes. If the source is increased in energy to 500 watt, and if the applicator is assumed to be about 80% efficient, the time taken to achieve this required temperature increase is approximately 15 seconds.